NOIDA INSTITUTE OF ENGINEERING &TECHNOLOGY

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VIKAS GUPTAEN-VI (B)

Hydraulic Accumulator

OVERVIEWIntroduction History Types of Hydraulic AccumulatorFunctions of AccumulatorAccumulator design consideration ApplicationConclusion

INTRODUCTIONA Hydraulic Accumulator is energy storage device. It is pressure storage reservoir in which a non-compressible

hydraulic fluid is held under pressure by an external source.The external source used can be a spring, a raised weight,

or a compressed gas.The main reasons that an accumulator is used in a

hydraulic system, is that the pump doesn’t need to be so large to cope with extremes of demand and supply circuit can respond quickly to any temporary demand and to smooth pulsation.

HISTORYFirst Hydraulic accumulator was made by

William Armstrong in 1846 built a crane powered by water of town mains at Newcastle, United Kingdom.

Later 1852 ,Armstrong used Grimsby Dock Tower for the constant pressure for cranes, lock gates and sluices.

Grimsby Dock Tower is hydraulic accumulator is used for the purpose of containing a 30,000UK gallon (136 m3) hydraulic wrought iron reservoir at a height of 300feet (91 m) to provide power for lock gates and cranes of Grimsby Dock.

1. Tower type accumulator

2. Raised weight accumulator

3. Compressed-gas accumulator

4. Spring accumulator

TYPES OF HYDRAULIC ACCULUMATOR

1. TOWER TYPE ACCUMULATORThe first accumulators for

Armstrong’s hydraulic dock machinery were simple raised water tower.

It uses hydraulic headIt delivers constant pressure to the

output

LONDON TOWER BRIDGE

2. RAISED WEIGHT ACCUMULATOR A raised weight accumulator

consists of a vertical cylinder containing fluid to the hydraulic line.

The cylinder is closed by a piston on which a series of weights are placed that exert a downward force on the piston and thereby energizes the fluid in the cylinder.

Gravity acts on the weight to pressurize the hydraulic system fluid, thus storing energy.

ADVANTGES :

Used to meet heavy industrial requirements.

Extremely high capacity at low cost.

Rugged and durable construction.

LIMITATIONS :

Extremely bulky and heavy.Problem in sealing.

Hydraulic engine house, Bristol Harbor.

3. COMPRESSED GAS ACCUMULATORIt is widely used accumulator in present

scenario.It is popularly known as “hydro-pneumatic

accumulator”. It apply force to the liquid by using a compressed gas that acts as the spring.

It uses inert gas (nitrogen) under pressure that provides the compressive force on fluid.

Oxygen is not used because oxygen and oil can form an explosive mixture when combined under pressure

As the volume of the compressed gas changes the pressure of the gas, and pressure of the fluid, changes inversely.

4. Spring type accumulatorIt uses the energy stored in springs to create a

constant force .The load characteristics of a spring are such

that the energy storage depends on the force required to compress s spring.

The free (uncompressed) length of a spring represents zero energy storage.

As liquid under pressure enters the cylinder, causing a spring to compress, the pressure on the liquid will rise because of the increased loading required to compress the spring.

HYDARULIC SYMBOLS

FUNCTIONS : Where are accumulators used?Accumulators can be applied creatively in any number of situations, including: Shock or pulsation dampening: An accumulator can

be used to cushion the pressure spike from sudden valve closure, the pulsation from pumps or the load reaction from sudden movement of parts connected to hydraulic cylinders.

Leakage compensation: An accumulator can be used to maintain pressure and make-up for lost fluid due to internal leakage of system components including cylinders and valves.

Thermal expansion: An accumulator can absorb the pressure differences caused by temperature variations in a closed hydraulic system.

Energy conservation

Improved response times: An accumulator (bladder type) has virtually instantaneous response time that can provide fluid very quickly to fast-acting valves such as servos and proportional to improve their effectiveness

Discharge valve, electric (optional)

Accumulator

P-portGauge portShut-off valve

Manifold Block

Pressure-reliefvalve

Discharge, manual

Adapter fitting, Flange

ACCUMULATOR DESIGN CONSIDERATION : (What must I know to size and select an accumulator?)Accumulator typeAccumulator volumeNominal hydraulic system pressureMinimum and Maximum hydraulic system

pressurePre-charge pressureRequired flow rateOutput volume capacityRecharge timeResponse timeFluid type

APPLICATIONSAccumulators are devices used to store fluid power to do the following:Agricultural Machinery & Equipment.Forestry Equipment.Oil Field & Offshore.Machine Tools and Off- Road Equipment.Mining Machinery & Equipment.Construction Equipment.Suspension in vehicles.

CONCLUSION So what are the benefits of using accumulators?

Lower installed system costs, accumulator assisted hydraulics can reduce the size of the pump and electric motor which results in a smaller amount of oil used, a smaller reservoir and reduced equipment costs.

Less leakage and maintenance costs, the ability to reduce system shocks will prolong component life, reduce leakage from pipe joints and minimize hydraulic system maintenance costs.

Improved performance, low inertia bladder accumulators can provide instantaneous response time to meet peak flow requirements. They can also help to achieve constant pressure in systems using variable displacement pumps for improved productivity and quality.

Reduced noise levels, reduced pump and motor size couple with system shock absorption overall machine sound levels and results in higher operator productivity.

Flexible design approaches. A wide range of accumulator types and sizes, including accessory items, provides a versatile and easy to apply design approach.

Reduced energy costs, cost savings of up to 33% are achievable in high performance industrial machinery using accumulators.

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